1. Field of the Invention
The present invention relates a lithographic apparatus and device manufacturing method.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate or part of a substrate. A lithographic apparatus can be used, for example, in the manufacture of flat panel displays, integrated circuits (ICs) and other devices involving fine structures. In a conventional apparatus, a patterning device, which can be referred to as a mask or a reticle, can be used to generate a circuit pattern corresponding to an individual layer of a flat panel display (or other device). This pattern can be transferred onto all or part of the substrate (e.g., a glass plate), by imaging onto a layer of radiation-sensitive material (e.g., resist) provided on the substrate.
Instead of a circuit pattern, the patterning device can be used to generate other patterns, for example a color filter pattern or a matrix of dots. Instead of a mask, the patterning device can be a patterning array that comprises an array of individually controllable elements. The pattern can be changed more quickly and for less cost in such a system compared to a mask-based system.
A flat panel display substrate is typically rectangular in shape. Lithographic apparatus designed to expose a substrate of this type can provide an exposure region that covers a full width of the rectangular substrate, or covers a portion of the width (for example half of the width). The substrate can be scanned underneath the exposure region, while the mask or reticle is synchronously scanned through a beam. In this way, the pattern is transferred to the substrate. If the exposure region covers the full width of the substrate then exposure can be completed with a single scan. If the exposure region covers, for example, half of the width of the substrate, then the substrate can be moved transversely after the first scan, and a further scan is typically performed to expose the remainder of the substrate.
An aerial image (looking up from the substrate) formed by the patterning device can be non-telecentric with respect to the surface of the substrate, can have a non-uniform intensity profile, can have a non-uniform polarization profile, or similar optical properties “errors.” Typically, through control of each individually controllable elements within an array of individually controllable elements formed on the patterning device, one of the parameters can be corrected. However, in order to correct for more than one of these parameters, sets of individually controllable elements within the array are controlled together. The sets can include, two, three, four, etc. individually controllable devices, sometimes called a super pixel. However, even when using these sets or super pixels, the optical property errors can only be reduced, but not always eliminated. Also, many mask-based patterns (e.g., phase shift masks, alternating phase shift masks) can be effectively emulated by a maskless lithography system.
Therefore, what is needed is a more effective and efficient patterning device architecture and control arrangement.